Re: [Ext2-devel] [RFC] fast EA for ext3

Andreas Dilger (adilger@clusterfs.com)
Sun, 18 May 2003 16:57:18 -0600


On May 18, 2003 17:04 +0000, Alex Tomas wrote:
> this patch implements possibility to store EA into inode body
> which may be larger 128 bytes in 2.5 kernel.

What Alex didn't mention was the reason why we developed this patch in the
first place - speed. Storing EAs in external blocks is slow, and if you
have a lot of inodes with external EAs it is fatal, as the EA blocks consume
so much RAM that they force all of the inode/directory data out of cache.

Some benchmarks (from Alex):
> environment for old EA: just mkfs'ed EXT3, inode size 128, 33000 files
> environment for fast EA: just mkfs'ed EXT3, inode size 256, 33000 files
>
> old EA fast EA
> add attributes 2m35.241s 1m4.151s (+142%)
> dump attributes 0m28.716s 0m13.466s (+113%)
> change attributes 2m42.108s 1m4.413s (+153%)
> remove attributes 1m15.373s 1m3.909s (+19%)

Some minor improvements could be made, such as not storing user EAs inside
the inode if there are system EAs that could be stored there.

Cheers, Andreas

--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/

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